Integrally formed current sensor device

ABSTRACT

A current sensor device for measuring a current, in particular for measuring a battery current in motor vehicles, including an electric resistance element on which the current can be determined by means of a voltage, and a first and a second connection element which are electrically connected to the resistance element and are arranged on different sides of the resistance element. The resistance element and the connection elements are integrally formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Phase Application of PCT International Application No. PCT/EP2014/053949, filed Feb. 28, 2014, which claims priority to German Patent Application No. 10 2013 203 760.0, filed Mar. 5, 2013, German Patent Application No. 10 2013 210 130.9, filed May 29, 2013, German Patent Application No. 10 2013 210 128.7, filed May 29, 2013 and PCT/EP2014/051755, filed Jan. 30, 2014, the contents of such applications being incorporated by reference.

FIELD OF THE INVENTION

The invention relates to a current sensor device for measuring a current, in particular for measuring a battery current in motor vehicles, and to a motor vehicle comprising a current sensor device according to the invention.

BACKGROUND OF THE INVENTION

In motor vehicles, electric motors are used for an extremely wide variety of functions, be it as a main drive unit in an electric car or be it, for example, as a drive unit of an electrical power steering system. In many cases, the use of electric motors requires the use of current sensors for accurately measuring the supply current supplied to the electric motors or charging currents supplied to batteries.

Commercially available current sensors with a shunt which is arranged between two electrically conductive connections and is connected to said connections are known. The shunt is composed of a material, such as Manganin® for example, which is distinguished in that the electrical resistance remains largely constant over large temperature ranges.

On account of the high cost pressure in the automotive industry, there is a need to further reduce the costs of producing the current sensor. In this case, firstly the material of the shunt and secondly the production steps form significant cost factors of the current sensor.

SUMMARY OF THE INVENTION

An aspect of the invention provides a current sensor device which can be produced at low cost.

One aspect of the invention is a current sensor device of the kind mentioned in the introductory part, wherein the resistance element and the connection elements are integrally formed.

An aspect of the invention is based on the fundamental idea of simplifying the design of the current sensor device by the connection elements and the resistance element being integrally formed in a one-piece part. The connection elements and the resistance element are formed from a single piece or monolithically and from the same material. In this way, it is firstly possible to dispense with the production step of connecting the resistance element to the connection elements. Furthermore, it is possible to dispense with an expensive material for the resistance element. A further advantage of the invention is that voltages between the connection elements and the resistance element no longer occur in the event of thermal expansion of the parts.

The current sensor device according to an aspect of the invention is preferably developed in that the resistance element and the connection elements are formed from a one-piece sheet metal element. In this way, the current sensor device can be punched out of a metal sheet and can be produced in fewer production steps. The expenditure on production, materials and tools is reduced to a minimum in this way.

The current sensor device is advantageously developed in that the resistance element has a cross section which is smaller than the cross section of the connection elements.

The current sensor device is advantageously developed in that the resistance element has a section which is in the form of a bar.

The current sensor device is advantageously developed in that the resistance element has at least one bent section.

An embodiment of the current sensor device according to the invention in which the resistance element has a section which is bent in a serpentine manner has proven particularly advantageous. The resistance element is advantageously in the form of a labyrinth in the region of the measurement section.

An embodiment of the current sensor device according to the invention in which the sheet metal element comprises copper is further preferred.

The current sensor device is advantageously developed by an evaluation unit for evaluating the voltage across the resistance element.

The current sensor device is advantageously developed by at least one temperature sensor for measuring the temperature at the connection element and/or at the resistance element.

The current sensor device is advantageously developed in that the electrical resistance of the resistance element can be determined depending on the temperature by means of the evaluation unit.

The current sensor device is advantageously developed in that the determined current value can be corrected by a thermally influenced current value fraction by means of the evaluation unit.

Another aspect of the invention comprises a motor vehicle comprising a current sensor device according to one of the preceding embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Further preferred embodiments can be found in the dependent claims and the following description of an exemplary embodiment with reference to figures, in which

FIG. 1 shows a perspective view of a first exemplary embodiment of the current sensor device according to the invention,

FIG. 2 shows a perspective view of a second exemplary embodiment of the current sensor device according to the invention,

FIG. 3 shows a perspective view of a third exemplary embodiment of the current sensor device according to the invention, and

FIG. 4 shows a perspective view of the abovementioned exemplary embodiments with an evaluation unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a first exemplary embodiment of the current sensor device 1 according to an aspect of the invention for measuring a current, in particular for measuring a battery current. The current sensor device has an electrical resistance element 40 in which the current I can be determined by means of a voltage. The current sensor device 1 also has a first and second connection element 30, 50 which are each arranged on different sides of the resistance element 40 and electrically connected to the resistance element 40. The resistance element 40 and the connection elements 30, 50 are integrally formed. In the exemplary embodiments, the current sensor device 1 is formed from a one-piece sheet metal element comprising copper, wherein the device 1 according to the invention is not limited to copper and other electrically conductive materials can also be used.

The connection elements 30, 50 are elongate and straight. At their ends, the connection elements 30, 50 each have a passage 31, 51 through which a connection pin or the like can be passed in order to electrically connect the current sensor device 1 to an electrical circuit. The resulting current flow I through the first connection element 30, the resistance element 40 and the second connection element 50 is determined on the basis of a voltage drop between two measurement points 42 a, 42 b on the resistance element 40 and an electrical resistance R of the resistance element 40.

The resistance element 40 and the connection elements 30, 50 are in the form of sections of the sheet metal element. The section of the resistance element 40 is located in the center of the sheet metal element between the sections of the connection elements 30, 50. The section of the resistance element 40 has a respective connection region 41 a, 41 b with a cross section which is identical to that of the connection elements 30, 50. The measurement points 42 a, 42 b by means of which the voltage drop across the resistance element is measured are located in the connection regions 41 a, 41 b.

Furthermore, the resistance element 40 has a section or a region 43 with a cross section which is smaller than the cross section of the connection elements 30, 50. In the exemplary embodiment from FIG. 1, this region is in the form of a rod and is straight. As an alternative to this, this region 43 is formed with at least one bent section in the second and third exemplary embodiments. In FIG. 2, the region 43 of the resistance element is serpentine, and in FIG. 7 said region 43 is in the form of an S-bend. As shown in the figures, different shapes of the resistance element 40 are feasible within the scope of the invention. In this case, the height or thickness of the resistance element 40 can, as shown in the exemplary embodiment according to FIG. 5, differ from the thickness of the connection elements 30, 50. However, said thickness can, as shown in FIGS. 6 and 7, also be the same as the thickness of the connection elements 30, 50.

In this way, a constant electrical resistance R of the resistance element 40 can be realized with different materials or with different dimensions of the current sensor device. The electrical resistance R of the resistance element 40 is usually designed to be 100 μΩ. Mechanically and thermally stable resistance elements 40 can be realized by means of the bent sections.

As shown in FIG. 4, the current sensor device 1 can be extended by an evaluation unit 70 for evaluating the voltage across the resistance element 40. The evaluation unit comprises a printed circuit board 71 which is inserted in a housing 72. The signals which are produced by the evaluation unit 70 can be retrieved by means of two connections 73.

The evaluation unit preferably has one or more temperature sensors 71 for measuring the temperature at the connection element 30, 50 and/or at the resistance element 40. To this end, the temperature sensors can be arranged directly on the printed circuit board 71. The use of optical temperature sensors, for example, is feasible.

The evaluation unit 70 is suitable for determining the electrical resistance R of the resistance element 40 depending on the temperature. The change in the electrical resistance of the resistance element 40 due to heating or cooling of the resistance element 40 is taken into account in order to allow more precise current measurement. As a result, the determined current value can be corrected by a thermally influenced current value fraction in order to determine the approximately actual current. Dispensing with a particularly temperature-resistant resistance material can be compensated for in this way. 

1. A current sensor device for measuring a battery current in motor vehicles, comprising an electrical resistance element on which the current can be determined on a voltage, and a first and second connection element which are each arranged on different sides of the resistance element and electrically connected to the resistance element, wherein the resistance element and the connection elements are integrally formed.
 2. The current sensor device as claimed in claim 1, the resistance element and the connection elements are formed from a one-piece sheet metal element.
 3. The current sensor device as claimed in claim 1, wherein the resistance element has a cross section which is smaller than the cross section of the connection elements.
 4. The current sensor device as claimed in claim 3, wherein the resistance element has a section which is in the form of a bar.
 5. The current sensor device as claimed in claim 3, wherein the resistance element has at least one bent section.
 6. The current sensor device as claimed in claim 1, wherein the resistance element has a section which is bent in a serpentine manner.
 7. The current sensor device as claimed in claim 2, wherein the sheet metal element comprises copper.
 8. The current sensor device as claimed in claim 1, further comprising an evaluation unit for evaluating the voltage across the resistance element.
 9. The current sensor device as claimed in claim 1, further comprising at least one temperature sensor for measuring the temperature at the connection element and/or at the resistance element.
 10. The current sensor device as claimed in claim 8, wherein an electrical resistance of the resistance element can be determined depending on the temperature by the evaluation unit.
 11. The current sensor device as claimed in claim 10, wherein the determined current value can be corrected by a thermally influenced current value fraction by of the evaluation unit.
 12. A motor vehicle comprising a current sensor device as claimed in claim
 1. 13. The current sensor device as claimed in claim 2, wherein the resistance element has a cross section which is smaller than the cross section of the connection elements.
 14. The current sensor device as claimed in claim 4, wherein the resistance element has at least one bent section. 